Disposable, absorbent articles such as diapers, incontinence articles, sanitary towels, training pants and the like are well know in the art. Typically, disposable absorbent articles comprise a liquid pervious topsheet that faces the wearers body, a liquid impervious backsheet that faces the wearers clothing, and an absorbent core interposed between the liquid previous topsheet and the backsheet. The absorbent core must often be capable of absorbing and handling relatively large volumes of fluid like urine or other exudates discharged from the body of the wearer, and especially relatively large fluid volumes discharged over relatively short periods of time. The absorbent core needs to be capable of acquiring, distributing, and storing discharges initially deposited on the topsheet of the absorbent article. Preferably the design of the absorbent core is such that the core acquires the discharges substantially immediately after they have been deposited on the topsheet of the absorbent article, with the intention that the discharges do not accumulate on or run off the surface of the topsheet, since this may result in inefficient fluid containment by the absorbent article which may lead to wetting of outer garments and discomfort for the wearer. In addition, preferably the absorbent core will have a design that facilitates the initially retained discharges to be transported away from the area of initial retention to the ultimate storage region, which should not become prematurely saturated and so that bulk of the absorbent material in the storage core is utilised effectively.
There have been many attempts to design absorbent articles or cores to improve the above requirements, in particular when further requirements were brought up with respect to a desired reduction of product bulkiness or thickness.
In particular, substantial effort has been spent against improving the fluid handling properties of the absorbent cores by adding fluid acquisition enhancing materials thereto.
Several patent publications deal with improvements of fluid handling performance by adding specially treated cellulosic material.
For example U.S. Pat. No. 4,898,642 of Moore et al. discloses special twisted, chemically stiffened cellulosic fibres and absorbent structures made therefrom.
EP 0 640 330 of Bewick-Sonntag et al. discloses the use of such fibres in a specific arrangement with specific superabsorbent materials.
EP 0 397 110 (Latimer) discloses an absorbent article comprising a surge management portion for improved fluid handling, having specific basis weights, acquisition times and residual wetness.
EP 0 359 501 (Cadieux) discloses an absorbent structure in general by exemplifying a feminine hygiene product with
a hydrophilic cover layer (in direct contact with the wearer) with low density and large porosity; PA1 a transfer layer with higher density, smaller pores; PA1 and a reservoir layer
such that gradients (continuous or stepwise) are generated; and such that fluid passes well between the regions.
Both-cover and transfer region tend to avoid fluid dispersion, but rather enhance transfer of the fluid to the next layer, whereas the reservoir layer also distributes.
EP 0 312 118 (Meyer) discloses an absorbent article with a fibrous topsheet with larger pores than the pores of the underlying transport layer, which in turn has lager pores than the underlying absorbent body. Further, the transport layer has to have a hydrophilicity which is less than the one of the absorbent core, and may generally be characterised as being substantially hydrophobic.
In EP 0 312 118 it is said that some liquid might remain in the transport layer and also the topsheet, so as to cause a wet feel on the surface. In order to overcome this problem, it is proposed in EP 0 312 118 to exploit the resilient compressibility of the transport layer, such that in use under the pressure exerted by the baby, the pores become smaller and then can dry out the topsheet and transport the fluid away.
The above prior art structures, however, while exhibiting an improved acquisition performance of the core, still suffer from a wet and damp feel on the surface of the total structures (i.e. on the topsheet), due to (in absolute measurements) small amounts of liquid remaining loosely bound in the topsheet, which however, are clearly identified by consumers negatively as "wet feel".
There is also the need to further improve the fluid handling properties of the total structure, in particular when moving to thinner products which often comprise high amounts of superabsorbent particles dispersed in relatively small amounts of fluff. Fluid acquisition and distribution properties indeed can suffer from relative lack of void spaces as well as from high superabsorbent concentrations.
Hence it is the object of the current invention, to provide absorbent cores allowing for a reduced amount of loosely bound fluid in the topsheet and resulting in a drier feel of the topsheet.
It is a further object of the invention, to enhance fluid acquisition properties of the absorbent cores even beyond existing structures, while not compromising on the topsheet dryness.